Thermostatic switch



Dec. 18, 1951 c. s. MERTLER THERMOSTATIC SWITCH Filed Feb. 7; 1948INVENTOR- a m 6 WW Patented Dec. 18, 1951 UNITED STATES PATENT OFFICE 18Claims.

This invention relates to thermostatic electrical switches and moreparticularly to improvements in thermostatic switches which are of thetype commonly known as semisnap acting.

Thermostatic electrical switches known to the art may be classified inaccordance with their operational characteristics as being one of threemain types. One of these main types includes those switches which areknown as snap acting because they employ springs and/or levers tooperate at least one of the electrical contacts with a positive snapaction at the instant the thermal responsive member reaches apredetermined temperature. Switches of this type have the advantages ofhigh current carrying capacity. long contact life and absence of circuitdisurbances which cause interference with radio reception. However, suchswitches are relatively expensive to manufacture and possess an inherentwide temperature diiierential between the openin and closing operatingtemperatures.

A second category of thermostatic electrical switches comprise thosewhich are known as the creep type because the electrical contacts areopened and closed relatively slowly under the sole influence of thebending of the thermal responsive member as the temperature thereofchanges. Switches of this type possess the ad-' vantages of low cost andrelatively small temperature differential but have relatively shortcontact life and cause considerable radio interference due to thefluttering, and consequent frying. of the contacts at the instant whenthey are either opening or closing. Moreover, the current carryingcapacity of thermostatic switches of this type is of a relatively loworder since high currents intensify the above mentioned disadvantages.

The third general type of thermostatic switches comprise those known assemisnap acting. Switches of this type are somewhat similar in constuction to the creep type but differ in operating principle in that thecontacts open with a small snap action. This snap act-ion results fromdisposing the thermal responsive member so that it is eiiective to exertboth a frictional and a motion producing force upon a member whichmovably supports one of the switch contacts. The frictional forceenables thethermal responsive member to store up a certain amount ofmotion producing energ before any movement of the movable contactsupporting member occurs. When the stored energy is suificient toovercome the frictionalforce the movable contact is actuated with asmall snap action and this mode of operation is effective in bothcontact opening and closing directions. Switches of this type combinethe desirable operating features of both the creep and snap acting typethermostatic switches while retaining the relatively low cost of thecreep type switches but without the undesirable functioningcharacteristics of the latter.

An object of this invention is to provide improved semisnap actingthermostatic switches which are simple and less expensive to manufactureand which have a greater snap action than prior switches of the sametype.

Another object of the invention is to provide improved thermostaticswitches of the semisnap acting type in each of which one of the switchcontacts is mounted on a supporting member for movement in oppositedirections relative to the other switch contact and biased to move inone of these directions and in which the thermal responsive member hasan angular extension for effecting actuating of the contact supportingmember with a semisnap action, the thermal responsive member beingsupported in a manner such that the snap action is greater than in priorswitches of the same type.

A further object of the invention is to provide improved thermostaticswitches of the semisnap acting type in each of which the thermalresponsive member is adapted to be entirely supported by the movablecontact arm intermediate the ends of the latter and to actuate thecontact arm with a snap action when the ambient temperature reaches apredetermined value.

A still further object of the invention is to provide improvedthermostatic switches of the semisnap acting type in which the thermalresponsive member is supported by and hinged to the movable contactsupporting member.

ber and extending substantially parallel therewith in spacedrelationship, and an extension disposed at an angle to the main portionwith the free end of the extension in engagement with the movablecontact supporting member, whereby flexing of the thermal responsivemember, as the temperature varies, exerts both substantiallyperpendicular and longitudinal forces upon the movable contactsupporting member so that the said flexing does not result in movementof the movable contact until sufiicient energy has been stored in thethermal responsive member to overcome the static friction between thesaid extension and the movable contact supporting member, whereupon thelatter and its contact are moved with a snap action relative to theother contact.

Another object of the invention is to provide improved thermostaticswitches of the type mentioned in the two preceding objects and furthercomprising adjustable means adapted to engage the main portion of thethermal responsive member intermediate its ends, whereby the snap actionis enhanced and the switches may be adjusted for operation at difierentpredetermined temperatures.

The invention also has as an object the provision of an improvedthermostatic switch of the semisnap acting type in which the thermalresponsive member comprises a main portion and an extension disposed atsubstantially right angles to each other and formed integrally from abimetallic bar or strip, the said main portion being hinged to aresilient contact-carrying member so as to extend substantially paralleltherewith in spaced relationship thereto, with the said extensionresting upon the resilient member for actuation of the latter inresponse to temperature changes.

A still further object of the invention is to provide an improvedthermostatic switch of the semisnap acting type in which the thermalresponsive member is a substantially U-shaped bimetallic element, oneleg of the bimetallic element being hinged to a resilientcontact-carrying member and the other leg of the element resting uponthe resilient member to actuate the latter,

in response to a predetermined change in temperature, with a snap actionas the result of friction produced between the said resilient member andthe said other leg of the bimetallic element, the snap action beingenhanced by the flexing of the legs of the bimetallic element.

The invention further resides in certain novel features of constructionand combination and arrangements of parts, and further objects andadvantages thereof will be apparent to those skilled in the art to whichit pertains from the following description of the present preferredembodiment thereof, and certain modifications, described with referenceto the accompanying drawing in which: v

Fig. 1 is a side elevational view of the present preferred form of athermostatic switch constructed in accordance with this invention, theswitch being shown in its operated position;

Fig. 2 is a bottom elevational view of the switch illustrated in Fig. 1;

Fig. 3 is a detached, side elevational view of the thermal responsivemember employed in the switch illustrated in Figs. 1 and 2; Y

Fig. 4 is an end elevational view of the thermal responsive member shownin Fig. 3, the view being taken from the left of Fig. 3;

Fig. 5 is a side elevational view of a modified form of thermostaticswitch constructed in accordance with this invention;

Fig. 6 is a side elevational view of another modified form ofthermostatic switch constructed in accordance with this invention;

Fig. 9 is a detached, side elevational view of yet another form ofthermal responsive member which may be employed in thermostatic switchesconstructed in accordance with this invention;

Fig. 10 is a bottom plan view of the thermal responsive memberillustrated in Fig. 9; and

Fig. 11 is a side elevational view of yet another form of thermostaticswitch constructed in accordance with this invention.

Referring first to Figs. 1 through 4 of the drawings. the improvedthermostatic switch illustratecl therein comprises a base memberpreferably formed of metal although other relatively rigid materialssuch as hard rubber, plastic or the like may be employed. Adjacent oneend, the base member 20 is provided with an opening through which thereduced diameter portion 2| of a mounting stud 22 passes with asubstantial clearance. One end of the stud 22 is provided with anintegral head 23 of larger diameter than the diameter of the opening inthe base member and an insulating washer 24 is positioned on the studbetween its head and the adjacent face of the base member 20. Theportion of the stud 22 projecting beyond the other face of the basemember 20 is provided with a terminal member or bracket 25' and aninsulating washer 26 is positioned on the stud between this terminalbracket and the base member. The end of the stud extending beyond theterminal bracket is peened over or otherwise deformed to rigidly connectthe stud and terminal bracket to the base member with the studelectrically insulated from the base member but electrically connectedwith the terminal bracket. The terminal bracket 25 may be provided withany suitable means for connecting an electrical conductor thereto. Forthis purpose, the bracket 25 is shown as provided with a tapped hole 21for receiving a screw by which a conductor may be connected. The outerface of the stud head 23 is provided with a layer of silver or othersuitable electrical contact material thereby providing one contact 28for the switch.

Cooperating with the contact 28, and movable to and from engagementtherewith, is a second contact 29 mounted upon one end of a resilientmember or arm 30 which is biased to normally efiect engagement ofcontact 29 with contact 28. The other end of the resilient member or arm30 is mounted upon the base 20 in spaced relationship therewith by amounting means generally designated 3 I. This mounting means comprises aheaded stud 32 the shank of which passes through an opening in theresilient member or arm 30 and through a spacing collar 33, theresilient member 30 being interposed between the head of the stud andthe collar 33. The shank of the stud also passes through an insulatingwasher 34, an opening in the base member 20, insulating washer 35 andterminal member or bracket 36, the end of the shank of the stud 32 beingpeened or otherwise deformed into engagement with the outer surfaceofthe terminal member 36 to hold the parts, just mentioned, rigidly uponthe base member 20. The

terminal member or bracket 36 may be provided with any suitable meansfor connecting an electrical conductor therewith. As shown in thedrawing, this means comprises a threaded opening' 31 for receiving aconnecting screw with which an electrical conductor maybe attached tothe terminal bracket. It will be observed that this bracket iselectrically connected with the resilient switch arm and contact 29through the shank of the stud 32, the latter and the bracket 34 beinginsulated from the base member 20 by the washers 34 and 35.

The resilient member or arm 30 is provided, intermediate the contact 29and the mounting means 3|, with a thermal responsive member, generallydesignated 38, which is hingedly connected with the resilient member andadapted to move the latter, together with its contact 29, when thethermal responsive member flexes in response to temperature variations.As shown in Figs. 1, 2, 3 and 4, the thermal responsive member 39comprises a substantially U-shaped element formed integrally from abimetallic strip or bar which is bent to provide a main portion 39 andleg portions or extensions 40 and 4|. The leg or extension 4| ispreferably provided with a pair oi spaced lugs or cars 42 which extendthrough correspondingly spaced openings in the resilient member 30adjacent the mounting means 3|, the lugs 42 being bent so that thethermal responsive member 38 is pivoted to the resilient member 30.Instead of providing ears or projections upon the leg or extension 4i ofthe thermal responsive member, it will be apparout that the hinging ofthe latter to the resilient member 30 may be accomplished in any otherwell-known manner. The thermal responsive member 38 is mounted, as justmentioned, on the resilient member or arm 30 in a manner such that themain portion 39 thereof extends between the base member 20 and theresilient member 39 in spaced relationship therewith and substantiallyparallel thereto, the undefiected or cold position of the thermalresponsive member being indicated by the dot-dash lines in Fig. 1 fromwhich it will be seen that the leg or extension 40 extends atsubstantially right angles to the resilient member 30, the end of theextension or leg 40 being adapted to engage the resilient arm or memberand also being free to move with respect thereto.

At point substantially intermediate the length of the main body portion39 of the thermal responsive member, the base 20 is provided with anopening for receiving an adjusting member 43, here illustrated as ashaft the lower end oi which is threaded into the threaded interior of aboss or sleeve member 44, attached to or integral with the base member20, and extending outwardly therefrom. The inner end of the adlustingmember or shaft 43 is provided with an insulating pin or projection 45which is adapted to abut the main portion 39 of the thermal responsivemember to limit the movement of the latter toward the base 20 andthereby regulate the operation of the switch as hereinafter described.Adjustment of the member 43 for effecting regulation of the switchoperation may be eifected by means of a conventional knob or the like,not shown, attached to the outer end oi the shaft 43, the extent ofadjustment being preferably limited by a radially extending proiection46 upon the shaft 43 which is adapted to abut an axially extendingprojection 41 provided upon the sleeve or boss 44 as is well known inthe art.

The switch illustrated in- Figs. 1 and 2 is such that the contacts 29and 29 are normally in engagement for temperatures below a predeterminedvalue, the contact 29 being moved relative to the contact 28 andseparated therefrom when the ambient temperature exceeds thepredetermined value for which the switch is set to operate.

Let it be assumed that the ambient temperature is below that for whichthe switch is set to operate its so that the thermal responsive member39 occupies the position indicated in the dot-dash lines of Fig. 1 andthe contacts 29 and 29 are in engagement. As the ambient temperaturerises the thermal responsive member, being bimetallic, will flex to aposition substantially as shown in full lines in Fig. 1. It will beobserved from this figure that the flexing of the thermal responsivemember results in a number of different movements of various portions ofthe said member. Thus the main portion 39 bows so that its centralportion engages the lower end of the projection 45, the said centralportion having moved a distance A. This causes the legs or extensions 49and H to be deflected relative to the resilient member 30 so that theleg or extension 40 tends to move longitudinally thereover, the extentof this tendency and the amount of the element movement in thisdirection being further increased by the inwardly bowing of the legs 49and 4| themselves due to the flexing thereof in response to thetemperature change.

The initial flexing of the thermal responsive member has resulted in afirm engagement of the free end of extension 40 with the resilientmember 30. it being remembered that the resiliency of the latter acts inthe direction for maintaining the contact 29 in engagement with thecontact 28. Hence, this initial flexing does not result in a movement ofthe leg or extension 49 relative to the resilient member 30 since thefriction produced by the engagement of this leg with the resilientmember prevents any relative movement therebetween until the energystored in the thermal responsive member by flexing thereof is slimcientto overcome the static friction between the leg 40 and the resilientmember 30. Since the static friction is much greater than slidingfriction, when the energy stored in the thermal responsive member insufficient to overcome the static friction, the leg or extension 4!!slides relatively rapidly in a longitudinal direction over the resilientmember 30 to substantially the position shown in solid lines in Fig. 1,this rapid sliding being in the nature of a snap action andresult ing inthe corresponding relatively rapid movement of contact 29 out ofengagement with contact 28.

With further reference to Fig. 1, it will be seen that the free end ofthe extension or leg 49 has moved a distance B in a longitudinaldirection along the resilient member 30, as the result of deflection ofthe legs or extensions 40, 4|, due to the flexing of the main portion39, plus the deflection of the said legs or extensions themselves due toflexing in response to temperature changes. In addition to this movementof the free end of the leg or extension 40, the bowing of the mainportion 39 and the bowing of the leg or extension 4| through a distanceC has caused the main body portion 39 to move a distance D relative tothe insulating pin or projection 45.

It will be seen, therefore, that the free end of the leg or extension 40exerts both a substantially perpendicular and a substantiallylongitudinal force upon the resilient member 39, the

perpendicular force being that which is eiIected to produce contactmovement while the longitudinal force is that which produces the snapaction. The novel construction results in greater longitudinal movementof the extension or leg 40 than is possible in prior art constructionsso that the snap action effect is increased. This insures longer contactlife and a more accurate -although a washer similar to switch has beenoperated as above described, the

thermal responsive member 38 tends to return to it initial position andhence the leg or extension 40 again tends to move longitudinally withrespect to the resilient arm 30. As in the case of the previouslydescribed movement in the opposite direction, the static frictionbetween the leg or extension 40 and the resilient member 30 initiallyprevents this relative movement until sum-cient energy has been storedin the thermal responsive member to overcome this static fric tion,whereupon the end of the extension 40 rapidly slides over the surface ofthe resilient member 30 so that the latter and its contact move with asnap action back to their initial position. The temperature at which theswitch operates, as just described, may be selected within apredetermined range by adjustment of the shaft 43 thereby regulating theposition of the abutment pin 45 relativeto the portion 38 of the thermalresponsive member. Other means of adjustment of the switch may bereadily effected if desired. For example, instead of employing anadjustable abutment for cooperation with the main portion 39 of thethermal responsive member, a fixed abutment may be employed and thecontact 28 mounted for adjustment relative to the base an.

member 20 in the same manner as described for the correspondinglynumbered parts illustrated in Fig. 1. As before, the contact 28 ismechanically and electrically connected with a terminal member orbracket 25 which is insulated from the base 20 by a washer 26, thecontact 28 and stud 22 being insulated from the base 20 by a strip orplate of insulating material 50,

Fig. 1, may be employed. Cooperating with the contact 28 is a movablecontact 29 mounted upon one end of the resilient member or arm 30. Themember or arm 30 is mounted upon the base 2') in substantially the samemanner as shown in Fig. 1, and hence corresponding parts are designatedby the same reference numerals. It will be observed, however, that theinsulating washer 34 is now replaced by a portion of the resilient plateor strip 50, although, as mentioned above, this plate or strip 50 may bereplaced by separate insulating washers 24 and 34 for cooperation withthe studs 22 and 32, respectively. The stud 32 is provided with aterminal bracket or member 36 connected with the stud 32 as previouslydescribed.

In the present form of the switch, however, the thermal responsivemember, generally designated is constructed differently from thepreviously described thermal responsive member 38. As shown in Fig. 5,the thermal responsive member 5| comprises a substantially straight mainportion 52 formed of a bimetallic strip orbar. Adjacent one end of themain portion 52 are connected 9. pair of spaced pins 53 which arerigidly connected with-the main portion 52 and have tapered lower 24, asshown inends for reception in, correspondingly spaced openings in theresilient member or arm 30. These openings in the resilient member 30are of sufficient size to permit tilting of the pins 53 therein thusproviding a hinged connection of the thermal responsive member to theresilient member or arm 30. The other end of the main portion 52 of thethermal responsive member is provided with a projection or pin 54rigidly connected with the main portion 52 and extending atsubstantially right angles thereto for engagement with the resilientmember 30. The pins 53 and 54 may be formed of any desired material butpreferably are non-conductive so that the current flowing through thethermostatic switch does not pass through the bimetallic main portion 52of the thermal responsive member.

The present form of the thermostatic switch is also provided with anadjustable abutment adapted to engage the main portion of the thermalresponsive member intermediate its ends and thereby regulate theoperation of the switch. This adjustment may be formed in the samemanner as shown in Fig. 1. As illustrated in Fig. 5, however, theadjustment member is shown simply as a threaded stud 55 the lower end ofwhich is provided with a projection or pin 56, preferably formed ofinsulating material, the stud 55 being screwed through a threadedopening in the base 20 and the outer end of the stud being provided witha slot or other suitable surface 51 for engagement with a screw driveror other tool.

A switch constructed as shown in Fig. 5 operates in substantially thesame manner as that illustrated in Figs. 1 and 2 except that theextensions or legs 53, 54 of the thermal responsive member 5| do notthemselves flex or bend in the construction illustrated in Fig. 5, thesole flexing occurring in the main body portion 52. Nevertheless, thisflexing of the thermal responsive member produces movements A, B, C andD as before, although the values of these several movements are somewhatdifferent than when the thermal responsive member is entirelyconstructed from bimetallic material. As before, the free end of theextension or leg 54 exerts both substantially perpendicular andlongitudinal forcesdash lines inthe same figure, will havecaused thefree end. of the extension onleg 54 to have moved a distanceBlongitudinally of the resilient member 30 and a distance Aperpendicularly thereof. The movement through the distance B is thatwhich produces the snap action while the movement through the distance Aeffects contact separation.

Fig. 6 illustrates a further modified form of thermostatic switchconstructed in accordance with this invention, the switch beinggenerally constructed in the same manner as illustrated in Fig. 5 andtherefore the same reference numerals are employed for correspondingparts which need not be again described in detail. In the present switchconstruction, however, the thermal responsive member, generallydesignated 60, is differently constructed and is hingedly connected tothe resilient member 30 in a somewhat different manner from thatillustrated and described ior the forms of the switches illustratedinFigs. 1 and 5. In the present construction, the thermal responsivemember 60 is a substantially L-shaped' bimetallic strip or element withthe main portion 8i thereof extending substantially parallel with andspaced from the resilient member 30 and with the free end of theintegral extension or leg 62 engaging the said resilient member 30. Theend of the main portion 6|, opposite to that which is provided with theextension 62, is provided with a pair of spaced openings which arefitted over reduced diameter portions 63 of correspondingly spaced pinsor projections 84, the other ends of which pins are rigidly connectedwith the resilient member 30. The openings in the portion if of thethermal responsive member are larger than the diameters of the extension83 of the-pins 64 so that the thermal responsive member can tilt orhinge relative to the pins 64, from its position as shown in full linesin Fig. 6 to that indicated in dot-dash lines in the same figure. Sincea switch constructed as shown in Fig. 6 operates in the same manner asthose described with reference to Figs. 1 and 5, it need not be furtherdescribed in detail except, to note that, in the present construction,the movement through the distance designated C in the previous figuresis no longer present. Nevertheless, the extension or leg 62 itselfflexes similar to the corresponding leg or extension in Fig. 1. Theswitch shown in Fig. 6 therefore operates with a snap action oi itsmovable contact 29 in substantially the same manner as previouslydescribed and hence need not be repeated.

Figs. 7 and 8 illustrate another modified form of thermal responsivemember whichmay be employed in switch constructions similar to thoseillustrated in Fig. 6 thereby producing switches having the same generaloperational characteristics. This form of thermal responsive element,generally designated 10, employs a substantially fiat bimetallic stripor bar ll forming the main portion of the thermal responsive element.One end of this portion H is provided with a pair spaced openings 12 forpositioning upon'extensions such as 63 of the pins '64 in a switchconstruction similar to that shown in Fig. 6, the

openings 12 being of larger diameter than the diameters of theextensions 63. The other end 01' the bimetallic strip or bar,constituting the main portion ll of the thermal responsive member, isprovided with a projection or pin 13 rigidly connected with thebimetallic portion and extending at substantially right angles therefromfor engagement with a resilient switch arm such as 30. This projectionor pin 13 corresponds in function and operation with the pin 54 in theconstruction shown in Fig. 5, or the integral extensions 40 and 62 shownin Figs. 1 and 6, respectively. A switch employing a thermal responsivemember 18 constructed as shown in Figs. 7 and 8 will also operate with asemisnap action, the principles thereof being the same as previouslydescribed. The snap action, however, will be less than that whichresults from the previously described constructions but nevertheless isstill suflicient for satisfactory operation in certain installations.

Figs. 9 and illustrate a still further modified form or thermalresponsive member which may be readily employed in switch constructionssimilar to those illustrated in Figs. 1 and 5. The present form ofthermal responsive member, which is generally designated 80, comprises abimetallic strip or bar bent to a substantially L-shape therebyproviding a main portion 8| and an extension or leg portion 82. Theextension or leg 82 is preferably provided with a pair of spaced,integral ears or projections 83 which are adapted to be received in thespaced openings of the resilient arm or bar 30 shown in Figs. 1 and 5.The

other end of the main portion M is provided with an extension or legmember 84, here illustrated as a pin rigidly connected with the mainportion 81 and extending at substantially right angles therefrom. Thelower end of this pin or extension 84 is adapted to engage and slideupon the resilient arm or member 30 in the same manner as the extensionsor legs 48, 54, 62 and I3 previously described, thereby producing asemisnap action of the contact 28 when the thermal responsive memberflexes in response to temperature variations. The operation of this formof thermal responsive member is substantially similar to those alreadydescribed and hence need not be repeated, it being suflicient to notethat, since the leg or portion 82 of the present form of thermalresponsive member is bimetallic, the movement of the pin or projection84 over the resilient member 30 is greater than in the case of thecorresponding projection of the thermal responsive member illustrated inFigs. 7 and 8 but less than that or the member illustrated in Fig. 1.

Fig. 11 illustrates a still different form of thermostatic switchconstructed in accordance with this invention. This switch alsocomprises a stationary contact 28 mounted by means 01' a stud 22 upon abase member 20 in the same manner as described for thecorrespondingly'numbered parts illustrated in Fig. 5. As before, thecontact 28 is mechanically and electrically connected with a terminalmember or bracket 25 which is insulated from the base by an insulatingwasher 26, the contact 28 and stud 22- being insulated from the base 20by a strip or plate of insulating material 50, although a washer similarto 24, as shown in Fig. 1, may be employed. Cooperating with the contact28 is a movable contact 28 mounted upon one end of a movable contactsupporting member or arm I38 biased to normally effect engagement ofcontact 29 with contact 28. As illustrated, this supporting member orarm is formed of relatively thin metal the previously mentioned biasingaction being atiorded by the resiliency of the member. The member or armI30 is mounted upon the base 20 in substantially the same manner asshown in Figs. 1 and 5 and hence corresponding parts are designated bythe same reference numerals. It will .be observed, however, that theinsulating washer 34, shown in Fig. 1, is now replaced by a portion ofthe resilient plate or strip 50, as in the construction shown in Fig. 5,although, as mentioned above, this plate or strip 50 may be replaced byseparate insulating washers 24 and 34 for cooperation with the studs 22and 32, respectively. The stud 32 is provided with a terminal bracket ormember 36 connected with the stud 82 and insulated therefrom by a washer35 as previously described. I

In the present form of the switch the thermal responsive member,generally designated 80, comprises a substantially U-shaped memberformed integrally from a bimetallic strip or bar so as to provide a mainportion 8| and angularly extending legs or extensions 92 and 83. Themain portion 8| of the thermal responsive member is provided with anopening ll through which freely passes the shank of a headed stud 94,the inner end of the shank of the stud being received in and held by aninsulating member 95 provided'in the lower end of an adjusting screw orshaft 96. The adjusting screw or shaft 96 is otherwise similar to thecorresponding element designated 43 and is similarly threadedly receivedin a threaded boss or sleeve 44 provided upon the base 20, rotation ofthe shaft or screw 96 being limited as before by a radially extendingprojection or lug 91 which is adapted to engage an axially extendingprojection 93 provided upon the sleeve or boss 44. Preferably? the stud94 is threaded within the insulating member 95. and is initiallyadjusted so that the thermal 're-' stud 94 without engaging either, thethermal responsive member being entirely supported by the member or armI30 upon which the ends of the extensions 92 and 93 rest. The thermalresponsive member 90 is prevented from rotative displacement relative tothe contact supporting member I30 in any suitable manner, one convenientmode being that illustrated in Fig. 11 as comprising integral lugs orears I3I struck up from the edges of the member I30 and ex-t tendingadjacent the sides of the extensions or legs 92 and 93. A switchconstructed as shown in Fig. 11 operates insimilar manner to thosepreviously illustrated and described except that in the present formboth of the extensions or legs 92, 93 cooperate in effecting switchoperation. This follows from the fact that the thermal responsive member90 is bimetallic throughout its entire length, and hence every partthereof flexes in response to variations in temperature, the flexed ordeflected condition of the thermal responsive member being somewhatsimilar to that of the member illustrated in Fig.1

- except that both the legs or extensions .92, 93

its movement in this direction, and the legs or extensions 92, 93 aredeflected relative to the member or arm I30 and tend to movelongitudinally thereover. The extent -of this tendency, and the amountof ultimate movement of the extensions in this direction, being furtherincreased by the inwardly bowing of the extensions or legs 92, 93themselves due to flexing .thereof in response to temperature change.

'I The initial flexing of the thermal responsive member results in afirm engagement of the free ends of the extensions or legs 92, 93 withthe member I30, it being remembered that the resiliency of the latteracts in the direction for maintaining the contact '29 in engagement withthe contact 28. This initial flexing does not'result in a movement of,the legs orextensions 92. 93 over the surface of the resilient .memberI30, however, since the static friction, produced by the engagement bythese legs with the member, prevents any relative movement .therebetweenuntil the energy stored in the thermal, responsive member is sufficientto overcome this static friction. Since the static friction is energystored in the thermal responsive memwith contact 28. switch it will beobserved that. due to the pres rapidly over the resilientmember I30 andthis rapid sliding, being in the nature of a snap action, results incorrespondingly relatively rapid movement of contact 29 out ofengagement In the present form of the ence ofthe stud 94, the main bodyportion 9I of the thermal responsive member does not shiftlongitudinally in the switch and hence there is no movementcorresponding to that indicated D in Fig. 1.

The switch illustrated in Fig. 11 willalso operate when the thermalresponsive member is initially positioned in spaced relationship withrespect to the contact carrying arm I30. That is to say, the switch maybe adjusted by adjustment of the screw or shaft 96 and/or stud 94 sothat the bimetallic member is normally "supported by the head of thestud with the ends the portion 9I' with the insulating member or button95 and a firm engagement, of the legs or extensions 92, 93 with theresilient member or arm I30. Further flexing of thethermal responsivemember then actuates the switch in a manner previously described.

Instead of employing a thermal responsive member'entirely formed tram asingle bimetallic strip such as illustrated in Fig. 11, a switch ofsimilar construction may be provided with a thermal responsivemember'formed of a plurality of different materials. For example, themember may have its main portion 91 formed from a substantially straightbimetallic strip or bar, the extensions or legs 92, 93 being separatemembers united therewith, as for example, insulating pins or buttonssimilar to 13 or 94, illustrated in switch in which pivotal connectionsto the resilient or flexible contact arm areemployed, the holes withwhich the lugs or pins cooperate to provide the hinging action are ofsufllcient size to substantially prevent binding at such points. In theform of the switch shown in Fig. 11 the ends of the thermal responsivemember 90 are free to move over the resilient contact arm and thecentral opening through the bight portion of the thermal responsivemember is sufllciently larger than the portion of the stud 94 passingtherethrough so as not to interfere with free flexing movement of thethermal responsive member, .Hence, in all embodiments of the inventionbe construed in the genericsense as here set forth.

While the present preferred form of construction of a thermostaticswitch, constructed in acand described in considerable detail, together.

with certain modifications, it will be readily apparent that the formsillustrated and described are intended as illustrative only sincenumerous variations and modifications may be made by those skilled inthe art. For example, the principles here illustrated and described maybe readily employed in switches whose contacts are normally open but areadapted to be closed upon a change in temperature. Moreover, while themovable contact supporting member has been illustrated as formed from astrip of metal, the natural resiliency of which eflects the necessarybiasing of the contact in one direction, it will be apparent that thesame result may be achieved with other means for mounting and biasingthe movable contact; Thus, the portion of the members 30 to which thethermal responsive members are hinged may be rigid and only the portionengaged by the extensions or legs 46, 54, 82, 13 or 84, and carrying thecontact 29, need be movable. Likewise, the portion of member I30 whichis engaged by the leg 93 need not be movable. Therefore, the inventionis not to be considered as limited to the exact details of constructionand arrangements of parts herein illustrated and described but only asrequired by the spirit and scope of the appended claims.

Having thus described my invention, I claim: 1. A thermostatic switchcomprising a first contact, a second contact, a member supporting saidsecond contact for movement in opposite directions to and fromengagement with the first contact and biased for movement in one of saiddirections, and asubstantially U-shaped thermal responsive memberfloatingly supported intermediate the ends of said supporting member andsubstantially aligned therewith, the said thermal responsive memberincluding a bimetallic main portion extending substantially parallelwith said supporting member and spaced legs extending angularly fromsaid main portion and directed towards the said supporting member,

supporting member until the thermal responsive member has storedsuflicient force by flexing thereof to overcome the static frictionbetween the supporting member and the said one leg whereupon the saidthermal responsive member moves the said supporting member and thecontact thereon relative to the first contact with a snap action, andmeans adapted to engage said main portion of the thermal responsivemember intermediate the ends thereof to limit the extent of movement ofsaid'main portion away from said supporting member when said thermalresponsive member flexes.

2. A thermostatic switch comprising a first contact, a second contact, amember supporting said second contact for movement in oppositedirections to and from engagement with the first contact and biased formovement in one of said directions, a substantially U-shaped thermalresponsive member floatingly supported intermediate the ends of saidsupporting member and substantially aligned therewith, the said thermalresponsive member including a. bimetallic main portion extendingsubstantially parallel with said supporting member and spaced legsextending angularly from said main portion and directed towards the saidsupporting member, at least one of said legs being adapted upon flexingof the thermal responsive member in response to variations intemperature to exert force upon said supporting member in directionsboth substantially parallel with and perpendicular to said supportingmember, means adapted to engage the said main portion of the thermalresponsive member intermediate the ends of the latter to limit theextent of movement of said main portion away from said supporting memberwhen said thermal responsive member flexes, and means to adjust the lastmentioned means to thereby ad- Just the switch operation.

3. A thermostatic switch comprising a first contact, a second contact, aresilient member supporting said second contact for movement to and fromengagement with the first contact, and a thermal responsive membersupported by and hinged to said resilient member intermediate the endsthereof and having a portion directed towards said resilient member toexert force upon said resilient member'in a direction to effect movementof said second contact relative to the first contact when said thermalresponsive member flexes in response'to variations in temperature.

4. A thermostatic switch as defined in claim 3 and further comprisingmeans to adjust said switch for contact operation at differentpredetermined temperatures.

5. A thermostatic switch as defined in claim 3 and and in which the saidthermal responsive member is substantially U-shaped with one of the legsthereof hinged to said resilient member and the other of said legsconstituting the said portion directed towards said resilient member.

6. A thermostatic switch as defined in claim 3 and in which the saidthermal responsive member is a substantially U-shaped unitary bimetallicelement with one leg thereof forming the said portion directed towardsthe said resilient member and the other leg of the element hinged tosaid resilient member.

7. A thermostatic switch as defined'in claim 3 and in which the saidthermal responsive member comprises a bimetallic bar forming a mainportion one end of which is provided with means for hinging it to saidresilient member, and the said portion of the thermal responsive memberwhich is directed towards the said resilient member is a non-bimetallicmember connected to the other end of said main portion and extending atsubstantially right angles with respect thereto.

8. A thermostatic switch .asdefined in claim 3 and in which the thermalresponsive member comprises a substantially L-shaped unitary bimetallicelement.

9. A thermostatic switch comprising a base member, a first contactmounted on said base 12. A thermostatic switch comprising a base member,a first contact mounted on said base member, a resilient member mountedon said adjustable means carried by said base member and adapted tocooperate with said thermal responsive member to adjust said switch forcon-' tact operation at difi'erent predetermined temperatures.

10. A thermostatic switch comprising a base member, a first contactmounted on said base member, a. resilient member mounted upon said basemember, a second contact mounted upon said resilient member for movementto and'from engagement with the first contact, a substantially U-shapedbimetallic member, means for hing'ing one leg of said bimetallic memberto said resilient member with the other leg thereof directed towards andin engagement with said resilient member, whereby flexing of saidbimetallic member in response to a temperature variation'causes the endof said other leg to exert both substantially perpendicular andlongitudinal forces on the said resilient member, the said longitudinalforce creating static frictionbetween the said other leg and theresilient member so that flexingof the bimetallic member is preventedfrom effecting movement of said resilient member until the flexing hasstored sufiicient energy in the bimetallic member to overcome the staticfriction, whereupon the resilient member and the contact carried therebyare moved with a snap action relative to said first contact, andadjustable means carried by said base member and adapted to cooperatewith said bimetallic member to adjust said switch for contact operationat different predetermined temperatures.

11. A thermostatic switch comprising a base member, a first contactmounted on said base member, a resilient member mounted on said basemember, a second contact mounted upon said resilient member for movementto and from engagement with the first contact, a substantially L-shapedbimetallic member, means for hinging one leg of said bimetallic memberto said resilient member in spaced relationship therewith and with theother leg extending substantially perpendicular to said resilient memberand in engagement therewith, whereby flexing of said bimetallic memberin responseto temperature variations causes the end of said other leg toexert substantially perpendicular and longitudinal forces on the saidresilient member, the said longitudinal force creating static frictionbetween said other leg and the resilient member so that flexing of thebimetallic member is prevented from efiecting movement of said resilientmember until the flexing has stored sufllcient energy in the bimetallicmember to overcome the static friction, whereupon the resilient memberand the contact carried thereby are moved with a snap action relative tosaid first contact, and adjustable means carried by said base member andadapted to cooperate with said thermal responsive member to adjust saidswitch for contact operation at different predetermined temperatures.

base member, a second contact mounted upon said resilient member formovement to and from engagement with the first contact, a bimetallicbar, non-bimetallic extension members provided adjacent the ends of saidbimetallic bar and ex-.

tending substantially at right angles therefrom. one of said extensionmembers being hinged to said resilient member and the other of saidextension members being directed towards the resilient member and inengagement therewith. whereby flexing of said bimetallic bar in responseto temperature variations causes the end of the other of said extensionmembers to exert both substantially perpendicular and. longitudinalforces on the said resilient member, the said longitudinal forcecreating static friction between the said other extension and theresilientmemher so that flexing of the bimetallic bar is prevented fromeffecting movement of said resilient member until the flexing has storedsuiflcient energy in the bimetallic bar to overcome the static friction,whereupon the resilient member and the contact carried thereby are movedwitha, snap action relative to said first contact, arid adjustable meanscarried by said base member and adapted to cooperate with saidbimetallic bar to adjust said switch for contact operation at differentpredetermined temperatures.

13. A thermostatic switch comprising a first contact, a second contact,a member supporting said second contact for movement in oppositedirections to and from-engagement with the first contact and biased formovement inFone of said directions, a substantially U-shaped thermalresponsive member fioatingly supported adjacent said supporting memberin a manner such that the ends of both legs of the thermal responsivemember are adapted to engage and move along the said supporting memberto effect movementof the latter, and means adapted to be engaged by thebight portion of said thermal responsive member to limit the flexing oithe said bight portion thereof away from said supporting member and toprevent bodily displacement of the thermal responsive memberlongitudinal of the saidsupporting member.

14. A thermostatic switch "comprising a first contact, an elongatedmember supported adjacent one end thereof for movement of the other endin opposite directions towards and away from said first contact andbiased for movement in one of said directions, a second contact mountedon said elongated member adjacent the said other end thereof insubstantial alignment with said first contact, the said elongated memberhaving a planar surface thereon intermediate the ends of the member. athermal responsive member fioatingly supported intermediate the point ofsupport of said elongated member and the said second contact, the saidthermal responsive member including a bimetallic main portion extendingsubstantially parallel with the said elongated member in spaced relationwith respect thereto and at least one extensionportion of substantiallength extending angularly with respect to said main portion anddirected towards said elongated member for engagement with the planarsurface on the latter, the said extension portion exerting force uponthe elongated member in directions both substantially parallel with andperpendicular to the latter upon flexing of the said thermal responsivemember 17 in response to variations in temperature, and means adapted toengage the said main portion of the thermal responsive memberintermediate the ends of the latter to limit the extent of movement ofsaid main portion away from said elongated member when the said thermalresponsive member flexes.

15. A thermostatic switch comprising a first contact, a second contact,means including a movable portion supporting said second contact formovement to and from engagement with the first contact, the said movableportion having a planar surface, a substantially U-shaped thermalresponsive member having a bimetallic main portion and spaced legportions disposed at an angle to said main portion, means hinging one ofsaid leg portions to said supporting means in a manner to dispose saidmain portion in spaced relationship to said supporting means and withthe end of the other of said leg portions adapted to engage the planarsurface in the movable portion of said supporting means and slidethereover in the direction of the hinging means, whereby flexing of saidthermal responsive member in response to a temperature variation causesthe end of said other leg portion to exert both substantiallyperpendicular and longitudinal forces on the said movable portion, thesaid longitudinal force creating static friction between the said otherleg and the said movable portion so that flexing of thethermalresponsive member is prevented from effecting movement of saidsecond contact until the flexing has stored sufficient energy in thethermal responsive member to overcome the static friction, whereupon themovable portion of the supporting means and the said second contact aremoved with a snap action relative to said first contact.

16. A thermostatic switch as defined in claim 15 and in which the saidmain portion and at least one of the leg portions of the thermalresponsive member are integral portions of a single bimetallic element.I

17. A thermostatic switch as defined in claim 15 and in which the saidmain and both leg portions of said thermal responsive member areintegral parts of a unitary bimetallic element.

18. A thermostatic switch comprising a first contact, a second contact,means including a movable portion supporting said second contact formovement to and from engagement with the first contact, the said movableportion having a planar surface, a substantially L-shaped unitarybimetallic element, and one or more members fixed to said supportingmeans and projecting substantially perpendicularly therefrom intohinging engagement with one portion of said bimetallic element in amanner permitting rocking movement of the latter with respect to saidprojecting members, the end of the other portion of said L-shapedbimetallic element being positioned to engage the planar surface on themovable portion of said supporting means and slide thereover in thedirection of said projecting members, whereby a temperature variationcauses both portions of the said bimetallic element to flex therebycausing the end of said other portion thereof to exert bothsubstantially perpendicular and longitudinal forces on said movableportion, the said longitudinal force creating static friction betweenthe said other portion 01 the bimetallic element and the movable portionof the contact supporting means so that flexing of the bimetallicelement is prevented from effecting movement of said second contactuntil the fiexing has stored sufficient energy in the bimetallic elementto overcome the static friction, whereupon the movable portion of thesupporting means and the said second contact are moved with a snapaction relative to said first contact.

CHARLES S. MERTLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,795,907 Thomas Mar. 10, 19312,020,538 Denison Nov. 12, 1935 2,054,558 Dederick Sept. 15, 19362,158,850 Campbell May 16, 1939 2,476,083 Clark July 12, 1949

